package com.pnnd.stream;

import com.sun.xml.internal.rngom.parse.compact.EOFException;

import java.io.IOException;
import java.io.OutputStream;
import java.util.List;

public class MultiplySegmentOutputStream extends OutputStream {

    private List<MemorySegment> segments;

    protected int start;
    protected int offset;
    protected int limit;

    public MultiplySegmentOutputStream(List<MemorySegment> segments,int offset){
        this.segments = segments;

        this.offset = this.start = offset;

        int len = offset;
        this.limit = 0;

        for(MemorySegment segment:segments){
            if(segment.size() < len){
                len -= segment.size();
            }else{
                this.limit = segment.size() - len;
                len = 0;
            }
        }
    }

    public int capacity(){
        return this.limit - this.start;
    }

    public int remain(){
        return this.limit - this.offset;
    }

    private int getIndex(){
        int result = this.offset;

        for(MemorySegment segment:this.segments){

            if(result >= segment.size())
                result -= segment.size();
        }

        return result;
    }

    private MemorySegment getSegment() throws EOFException {
        int result = this.offset;

        for(MemorySegment segment:this.segments){

            if(result > segment.size())
                result -= segment.size();
            else
                return segment;
        }

        throw new EOFException();
    }

    private void checkReadLen(int len) throws EOFException {
        if(this.offset+len > this.limit){
            throw new EOFException();
        }
    }

    @Override
    public void write(int b) throws IOException {
        this.checkReadLen(1);

        MemorySegment segment = this.getSegment();

        int index = this.getIndex();

        segment.put(index,(byte)b);

        this.offset++;
    }

    /**
     * Writes <code>b.length</code> bytes from the specified byte array
     * to this output stream. The general contract for <code>write(b)</code>
     * is that it should have exactly the same effect as the call
     * <code>write(b, 0, b.length)</code>.
     *
     * @param      b   the data.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.OutputStream#write(byte[], int, int)
     */
    @Override
    public void write(byte b[]) throws IOException {
        write(b, 0, b.length);
    }

    /**
     * Writes <code>len</code> bytes from the specified byte array
     * starting at offset <code>off</code> to this output stream.
     * The general contract for <code>write(b, off, len)</code> is that
     * some of the bytes in the array <code>b</code> are written to the
     * output stream in order; element <code>b[off]</code> is the first
     * byte written and <code>b[off+len-1]</code> is the last byte written
     * by this operation.
     * <p>
     * The <code>write</code> method of <code>OutputStream</code> calls
     * the write method of one argument on each of the bytes to be
     * written out. Subclasses are encouraged to override this method and
     * provide a more efficient implementation.
     * <p>
     * If <code>b</code> is <code>null</code>, a
     * <code>NullPointerException</code> is thrown.
     * <p>
     * If <code>off</code> is negative, or <code>len</code> is negative, or
     * <code>off+len</code> is greater than the length of the array
     * <code>b</code>, then an <tt>IndexOutOfBoundsException</tt> is thrown.
     *
     * @param      b     the data.
     * @param      off   the start offset in the data.
     * @param      len   the number of bytes to write.
     * @exception  IOException  if an I/O error occurs. In particular,
     *             an <code>IOException</code> is thrown if the output
     *             stream is closed.
     */
    @Override
    public void write(byte b[], int off, int len) throws IOException {
        if (b == null) {
            throw new NullPointerException();
        } else if ((off < 0) || (off > b.length) || (len < 0) ||
                ((off + len) > b.length) || ((off + len) < 0)) {
            throw new IndexOutOfBoundsException();
        } else if (len == 0) {
            return;
        }
        for (int i = 0 ; i < len ; i++) {
            write(b[off + i]);
        }
    }

    /**
     * Flushes this output stream and forces any buffered output bytes
     * to be written out. The general contract of <code>flush</code> is
     * that calling it is an indication that, if any bytes previously
     * written have been buffered by the implementation of the output
     * stream, such bytes should immediately be written to their
     * intended destination.
     * <p>
     * If the intended destination of this stream is an abstraction provided by
     * the underlying operating system, for example a file, then flushing the
     * stream guarantees only that bytes previously written to the stream are
     * passed to the operating system for writing; it does not guarantee that
     * they are actually written to a physical device such as a disk drive.
     * <p>
     * The <code>flush</code> method of <code>OutputStream</code> does nothing.
     *
     * @exception  IOException  if an I/O error occurs.
     */
    @Override
    public void flush() throws IOException {

        this.innerFlush(this.offset);

        Object owner = this.getSegment().getOwner();

        if(owner instanceof MemorySegmentContainer){
            ((MemorySegmentContainer) owner).refresh(this.offset);
        }

        this.start = this.offset;
    }

    protected void innerFlush(int offset){

    }

    /**
     * Closes this output stream and releases any system resources
     * associated with this stream. The general contract of <code>close</code>
     * is that it closes the output stream. A closed stream cannot perform
     * output operations and cannot be reopened.
     * <p>
     * The <code>close</code> method of <code>OutputStream</code> does nothing.
     *
     * @exception  IOException  if an I/O error occurs.
     */
    @Override
    public void close() throws IOException {
        this.flush();
    }
}
